Sökning: "lift-up effect"

Hittade 4 avhandlingar innehållade orden lift-up effect.

1. 1. Study of generation, growth and breakdown of streamwise streaks in a Blasius boundary layer

   Författare :Luca Brandt; KTH; []
   Nyckelord :Fluid mechanics; laminar-turbulent transition; boundary layer flow; transient growth; streamwise streaks; lift-up effect; receptivity; free-stream turbulence; streak instability; secondary instability; Direct Numerical Simulation.;

   Sammanfattning : Transition from laminar to turbulent flow has beentraditionally studied in terms of exponentially growingeigensolutions to the linearized disturbance equations.However, experimental findings show that transition may occuralso for parameters combinations such that these eigensolutionsare damped. LÄS MER

3. 2. Stability analysis and transition prediction of wall-bounded flows

   Författare :Ori Levin; KTH; []
   Nyckelord :Boundary layer; wall jet; algebraic growth; exponential growth; lift-up effect; streamwise streaks; Tollmien-Schlichting waves; free-stream turbulence; roughness element; transition prediction; Parabolized Stability Equations; Direct Numerical S;

   Sammanfattning : Disturbances introduced in wall-bounded .ows can grow andlead to transition from laminar to turbulent .ow. In order toreduce losses or enhance mixing in energy systems, afundamental understanding of the . LÄS MER

4. 3. Numerical studies of bypass transition in the Blasius boundary layer

   Författare :Luca Brandt; KTH; []
   Nyckelord :Fluid Mechanics; laminar-turbulent transition; boundary layer flow; transient growth; streamwise streaks; secondary instability;

   Sammanfattning : Experimental findings show that transition from laminar toturbulent ow may occur also if the exponentially growingperturbations, eigensolutions to the linearised disturbanceequations, are damped. An alternative non-modal growthmechanism has been recently identi fied, also based on thelinear approximation. LÄS MER

5. 4. Optimisation and control of shear flows

   Författare :Antonios Monokrousos; Dan S. Henningson; Laurette Tuckerman; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; shear flows; flow control; optimal disturbances; Lagrange method; transition to turbulence; non-linear dynamics; Engineering mechanics; Teknisk mekanik;

   Sammanfattning : Transition to turbulence and flow control are studied by means of numerical simulations for different simple shear flows. Linear and non-linear optimisation methods using the Lagrange multiplier technique are employed. LÄS MER